Lift trucks are widely used to transport goods in warehouses, factories, etc. One common type of lift truck has forks especially adapted for insertion under a pallet for lifting the pallet and its contents. Another common type of lift truck has opposing clamps for grasping and lifting items, such as boxes, by the sides. The problem with clamp type lift trucks is that the clamping force is critical; too little force will allow the item to slip from the grasp of the clamps, while too much force may damage the item.
Lift truck clamps can be large for certain uses. For example, clamps for moving refrigerators or other large appliances may be three feet by four feet. The clamping force problems are exacerbated by larger sized clamps because clamp balancing becomes a potential problem in addition to total clamp force. A clamp balancing issue may exist when area of a clamp, such as the top area or the forward area, is applying more of a force to the grasped item that another areas.
To alleviate some of the force balance problems with large clamps, it is common to utilize pivotable platens. Such pivotable platens alleviate but do not resolve all of the force balancing problems. Various tests have been devised to measure total clamping force. Single point testing has been done using hydraulic pressure gage. This measures total clamping force but not force distribution. No adequate test is known to adequately measure and analyze both total force and force balance.